1. Field of the Invention
The present invention relates to a flywheel electric generator utilizing rotational kinetic energy of a flywheel.
2. Description of the Related Art
As is well known, the flywheel electric generator is an electric generator to store electric power in a flywheel provided for a rotor of the electric generator, as kinetic energy, so as to discharge the kinetic energy as the electric power. That is, the flywheel electric generator employs an energy storage system by which electric energy is converted into rotational energy of an object having large inertia moment to output and input the electric power. In general, the flywheel electric generator is often utilized to supply electric power to a load in need of pulse-like large electric power.
For instance, a nuclear fusion system confining plasma by means of a magnetic field supplies electric power of several hundreds of thousands kW in a short time such as several seconds sometimes, so that it is disagreeable to directly obtain such pulse-like electric power from an electric power system because the influence on the power system is too considerable. Therefore, such a filed of the electric power system employs the flywheel electric generator. The flywheel electric generator operates in such a cycle that it increases the number of rotations of an electric generator over a time period of several minutes to store the kinetic energy in the flywheel, and discharges the kinetic energy stored in the flywheel in supplying the electric power to a load to result in a decrease in the number of the rotations of the electric generator.
As to the conventional flywheel electric generator, a flywheel electric generator which uses a high-temperature superconductor for a magnetic bearing is proposed other than a flywheel electric generator which attaches a flywheel to a usual electric generator and operates in the atmosphere by using a usual bearing (e.g., refer to Jpn. Pat. APPln. KOKAI Publication No. 6-303738).
However, the flywheel using the high-temperature superconductor as the magnetic bearing is not a good idea because it needs to store the flywheel electric generator in a sealed container, makes a whole of the apparatus be complex and large in size and also takes a lot of trouble in work of maintenance and check and in restart after the maintenance and check.